Concurrently theoreticians, beginning with Lord Kelvin,^* have 

 tried to solve the problem of the wave resistance of floating bodies by classi- 

 cal hydrodynamic methods. Starting with the simplest abstractions, which are 

 suitable to describe the . phenomena only in the most general and tentative way, 

 they developed theories which are claimed to be useful for practical design 

 work. No clear conclusion has yet been reached as to how far this claim is 

 justified. Some scientists V7ho have made important contributions to the sub- 

 ject hold the opinion that the existing theories give only a good qualitative 

 picture of the actual facts, while other authors claim that close quantitative 

 agreement can be reached . 



In 1925, Professor Havelock delivering a lecture on "Some Aspects 



77 



of the Theory of Ship Waves and Resistance" quoted a paragraph from Kelvin's 

 famous paper on ship waves ("I made it a condition to the Council that no 

 practical results were to be expected from it. I explained that I could not 



say one word to enlighten you on practical subjects ") and appropriated 



this statement to his own work. Havelock could well afford to underestimate 

 the practical Importance of his work because it is in fact his paper, to- 

 gether with a contemporary article by C. Wlgley,*^ that marks the beginning 

 of the application of theory to practical discussions on wave resistance The 

 lecture mentioned and Wigley's reviews on the subject are recommended for 

 study to all students of the subject.**'*^ 



The present paper is to be judged from the viewpoint of how far it 

 is able "to enlighten on practical subjects.. j" its purpose is to show to 

 what extent theory has succeeded in furnishing valuable practical results and 

 how the scope of its applications can be extended. It is not a treatise on 

 hydrodynamics dealing with problems of free-surface effect; rather an attempt 

 to reconsider a basic phase of theoretical naval architecture in the light of 

 hydrodynamics. It bears by necessity a somewhat programmatic character be- 

 cause the tedious computations connected with the evaluation of the theoreti- 

 cal work have been initiated but not yet completed. 



There is common agreement that theory has furnished a valuable de- 

 scription of general phenomena; it is less well known that it also has given 

 us the proof of considerable practical value of how sensitive wave resistance 

 can be to changes, even small changes, in ship form. 



Experienced experimenters are often somewhat bewildered by the fact 

 that the wave resistance may vary appreciably for different but reasonable 

 types of lines, although all the form parameters generally considered as de- 

 cisive are Identical. Prom a theoretical viewpoint this appears to be quite 



♦Eeferences are listed on page 97. 



